Method and product for preventing efflorescence in ceramics



Patented Dec.16 1930 v V ART HU R ceramicarticle s, and relates furthertbg prev'ent 'ng eiflorescence or scummingbytheuse ofbarium s1l1cate.

"In the manufacture of ceramics jangl' ticula'rly' 1n the manufactureof br clgg barn.

' um fluoride, carbonatefchlcrideuiand hydrox-x ide have beenql eretofbre 'employedto pre-; a vent hat is kno'vvnLas efllorescfenc'e and scum-.

ming by virtue of theinteralction of these 15 compounds with the-sulphates and other fcompounds contained in' 1the."clay or vvater used. Thejsulphates my falso be formed 'upon the surface: of thelbrick or other :ceramic, article during thefburning by the conj densation of sulphuric acidunonthem from; the heating gases orby the direct action. of

sulphur trioxidel; which s is usually contained in the heating gases; Amongthe sulphates which commonly produce effiorescence are 25 calcium and magnesium sulphates.

The barium compounds, such as the fiuventing efilorescence andscumming, are relis used according to the presentinventionis and suitability.

in ceramic manufacture, and particularly in the manufacture of bricks, tiles,.terra-cotta,

V sewer pipes and other products made of'clay or similar materials. The action of barium sllicate (BaS1O in preventlng eifiorescence and scumming is indicated in the following equation wherein calcium sulphate, an 'ef-' fiorescence and scum. producing comp'ound, I y p Y preparedby fu'singbarium'sulphatelnative "bary tesl'Lvvith silica-{for example tsai d- The V v f'temperatures at hichth'esemateri'als inter- The reaction takes place during the heating I of the articles and results in the production: peraturelproduced by the vblast furnace and I of the very insoluble barium sulphate and calcium silicate Which is also highly insolis taken as illustrative 103mm.yasarnnoueriass eivoa rro sa n riaaarsoizr e I mmiioniiivn raonuo'r rorvrnnvEN'rINe;nrrrloimscnucn 111v cnnaiiics time! T e atchestfiaeleaaoa mass- 1 productswillfollowl' a I} I V jThe barium silicateisjpreferably "added in v the finely divided conditionflto the -mass or clay u es to make a the particular ceramic 1 pnoduct desired, Generallyspeaking-about the same quantity foffiba'ri-um silicate is] revnew used cfbarium roughapproximation, the amountof'barium 1 silicate might vary. anywhere jfroni 12 to 7 :Tpoun'ds per-[1,000 bricks, but" these propor- V oride carbonate, chloride and hydroxide;- which have heretofore been used for preatively costly and the barium silicate'vvhich' accordance with the present invention. jbarium slllcate ls-used to prevent scummlng noueiuor UMMIT; newsman, AND Joni: Georges iia-nn soixr i fore lbeipraictically insoluble, and. if the pro- V portionsgo'f the ingredients; are ;areu11y; ad-- 1 justed so as 01? to have aqqgmeaa excess of a the. barium "silicate; an efiactl balance of the quired in bricks and ceramics, generally as is carbonate, HoWe'ver, 1t

will;beappreciatedthat chemists generally, to determinejthejexact amount ofba'riumfl sil'cate 7 required to f comsulphate contentfof tlie:bricksjas explained above. It should alsofbeunderstood that-the solublesaltcontent of the water used inmak; ing-thefceraniic products-statue be takeninto @CCOlljfit llIl calculatingthe'amount of barium gsilicatei'a's these esaltsjare'fadded tojthe clay ai t The-addition of thefine'ly divided barium her mass 'vvhenfthe v'vat erfj is" addedito snail-teta us be accompa ied by thorough mixing sofas to uniformly distribute it" 7 through the ceramic mass before baking or burning. The formation of the ceramicmass hence' the reaction. may be causedf to take place in such a furnace; The reaction takes a he q a i ityfiqfb 7 jum silicate depends entirely onjth'e soluble salts in the clay and these varyf The'practia m thod of determining the: amount for barium 'si licajte is to analyze the clay for the soluble salts suchlas sulphates,andthenfit'is simple: chemical; calculation, 3 known to 7 and1;the baking or A burning takes place in the .lusual manner;

equation: a

place in accordance, with the following Ifhepr oprt-ions of barium sulphate and silicon dioxide (figured as pure material's) called for by'this equation maybe used, f-

.60.3 parts of silicon dioXideL' The reag'ent'sf "are:preferably-used in a'pulveriz ed condition and the reactiongtakesgplace; at about 1300?;

' r i C. It is to beunder'stoodthat forms of silica other itha-nlwsand can be usedyfor' example ,kieselguhr; -The reaction mayalsobe; car- 7 same heateintensityi Thereaction can also namely 233.44 parts of barium sulphate and ried out man electric-f furnace providing the i becarried out by heating a mixture of sand and'finely divided barium sulphate in'a cru- 1 cible to theipoi'nt of fusion or to about 1300 and holdingjthetemperature at that point 7 [until the reaction'hasgoneto'completion;

It will be seen-from the above reaction of bariumsulphate andv silica: that sulphur tri- 'derstood by a'personskilled in the art and no detailed explanation of how they should jMostbommercial barytes contain a conoxide is produced, This: gaseous product Q may be condensed in water to produce sul-. phuric acid "as a. 'by-product. The collection of these gasc's'oi' fumes will be readily un-' be collected is believed to be" necessary.

siderable quantity of silica and this I quanthis will gotowards "tity of silicalmust'be considered; in the calculation of theamount ofl sand {or silica to be mixedwiththebarytes for fusion; Then again, the actual content of BaSO; must be,

' calculatedin theraw barytes and the amount ofsand or silica calculatedfromthis. It Hwill be seen, theref0re,that bythis process n V the percentageofsand'orl silica in-the raw" barytes" may bea advantage, inasmuch as b p yed. mnta ns y i barium Y carbonate,

to the particular barium silicate indicated bythe chemical equation given. We have found however that'the product of the reaction does have utility in therelationships defined and hence hasutility independently of knowledge of the exact compound produced, It is thereforeftobeunderstood that "byjbarium' silicate we mean barium silicates generally incontradistinction to any particular} barium silicate.

; -Having described ouri nvention what we claim is e "2. The process of prevent ng efliorescence or scumming in baked or burned silici'ous ma- L. 1-1; The'iprocess oflpreventing 'efilorescence or scumming n ceramlcs which comprises addlligfbai'iumslllcate tothe material from whlchthe ceramics are made terial which comprises adding silicate of barium to the silicious mass prior to baking ur -g In the; art "of preventing efilores'cen'ce inthe manufacture o f'cerami'c's' and glass,lthe addition to the batch, prior to baking, of

barium silicate as an agent for preventing efilore'scence'or scummmg". v

.4. As an intermed its product, an un baked ceramic article having finely divided barium silicate distributed throughout the process for. preventing efflorescence or scumming- 1n ceramic materlal which comprises adding toithe unbaked ceramicmate- 'rial a barium sih c'ate whichiis insoluble in cold water and decomposes in hot water.

In testimonyv whereofwelaflix our signatures.w,.." c ARTHUR HOUGH. V I J GEORGE HARRISON.

cate isso employed a glass ofvery high re- ,fractive indeX,0f great brilliance,'together with unusual toughness is'produ'ced. 'As infbonatein these "applications, v 5 7 dicated'above, thebarium silicate may also be useclwith exceptionally good 1138111135111" the manufacture of sanitary enamel ware "and enamel and is used substantially in the" same manner and proportions as barium 'car- .{NVhile we have i dicated abovefthe reaction which we believe to take'place between barium sulphate andsilica', yet it is quite possible that another era series of barium,

' silicates'may beformed,and we do not wish it to be understood that we limit ourselves 

